In Illustrator, are you working in RGB or CMYK? If you're working in a different color profile than the intended end destination you're going to get some variation because of the translation. If you can figure out what your "final destination" is you can apply that in Illustrator and you shouldn't have this problem.

I can confirm that the situation as stated in the original question occurs in Illustrator CS3 when working with a CMYK document, and that it does not occur when working with an RGB document. I have all color profiles disabled to the extent possible.
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horatioApr 7 '11 at 20:43

@mattalexx, I don't know what to tell you. I can't reproduce your error. One thing I did notice, if I set the color of the object to AB336B (in RGB mode), then switched it to CMYK, then straight back to RGB the color had changed to AB326B. I'm using CS5, btw. However, the difference between CA006C and AB336B is huge, so I have no idea what is going on. Can you duplicate the problem with a fresh file? If so, what steps did you use?
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SamApr 8 '11 at 20:09

There's a few important points required to ensure colours are correctly maintained when working on web or app designs in Illustrator. Some of the settings below affect the appearance of the preview within Illustrator, while other affect the appearance of the exported files.

In my opinion, it is important both are correct. Here's what you'll need to do:

Ensure the document is set to RGB colour space (not CMYK).

Appearance of Black under Preferences is set to “Display All Blacks as Rich Black”.

I completely disagree with this. But to each his own. I recommend some browsing: digitaldog.net
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ScottMar 13 '13 at 18:28

The issue with that site, is that it’s for photographers. A different approach is needed for UI and web design.
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Marc EdwardsFeb 17 at 9:23

Color is color. It makes no difference if you are viewing a photograph or a ui. That's a very weak argument.
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ScottFeb 17 at 15:29

Nope. The main difference is that UI typically isn’t colour managed — if you provide a file with an ICC profile and pixel that’s #ff0000, then iOS, OS X and Android will display it as #ff0000 with no conversion. If you do the same for a JPEG photo on the web or for print, the profile will be used to convert to the display’s colour space. They are absolutely NOT the same. People who argue they are clearly have no UI design experience.
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Marc EdwardsFeb 20 at 22:59

It’s also worth noting that profile conversion is a bad thing. It often leads to rounding (visible as banding) and clipping. If you can create with your display set up as sRGB with no conversion, you’ll be better off for it. Print design is not the same as UI design when it comes to colour management.
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Marc EdwardsFeb 20 at 23:01